1. Field of the Invention
The present invention relates to a plasma etching apparatus for carrying out a manufacturing process of plasma etching.
2. Description of the Background Art
A plastic mold opening device such as that disclosed in Japanese Patent Application Laid Open No. 63-296229 has been known conventionally for opening up a device under test such as an IC chip in order to enable the analysis of malfunctions.
In a case where a further detail analysis of the interior of the IC chip is required, it is necessary to remove the passivation film on a chip surface. By removing the passivation film, it becomes possible to carry out the analysis operation to identify electrically malfunctioning parts by using a probe connected with a curve tracer or an oscilloscope. Also, if it is possible to use an electron microscope, the state of voltage level of each part of the chip can be comprehended without a contact by taking an electron micrograph of the chip in an operating state, so that the malfunctioning parts can easily be identified.
In general the passivation film of the chip is made of a surface layer of silicon nitride (Si.sub.3 N.sub.4) film and an inner layer of phosphosilicate glass (PSG) film. As a method for removing such a passivation film, a wet method and a dry method have been known conventionally.
In the wet method, the phosphoric acid solution heated up to approximately 180.degree. is used for removing the silicon nitride film, and the buffered hydrofluoric acid (ammonium fluoride solution) at the room temperature is used for removing the phosphosilicate glass film.
In the dry method, the silicon nitride film is removed by the dry etching due to a mixed gas of carbon tetrafluoride (CF.sub.4) and oxygen in an isotropic plasma etching apparatus, and the phosphosilicate glass film is removed by the dry etching due to a mixed gas of carbon tetrafluoride (CF.sub.4) and hydrogen, or a gas of a compound having a smaller ratio of C and F such as C.sub.3 F.sub.8 in an anisotropic plasma etching apparatus.
The plasma etching apparatus used in the dry method has a table provided on a base, which functions as an electrode, and on which a device under test such as an IC chip to be applied with the etching process is placed, and a freely openable chamber lid having another electrode to cover the device under test from above is provided over the table. In this plasma etching apparatus, the etching process can be applied to the device under test by supplying a gas to the discharge chamber formed by the table and the chamber lid in a state in which the chamber lid is closed and the device under test is placed between two electrodes, and by causing the plasma generation between two electrodes.
Now, in such a conventional plasma etching apparatus, although the device under test is fixed on the table, the pins of the IC chip in mutually insulated state can lead to the damaging of the IC chip during the etching process due to the differences among the voltage levels produced on the pins, so that it is necessary to maintain the pins at the same voltage level. Conventionally, this has been achieved by providing holes or grooves with constant interval in correspondence with the pins such that the pins can be fitted into the holes or grooves in order to prevent the generation of the voltage level differences.
On the other hand, in order to prevent the deterioration of the reproduction capability of the IC chip due to the variations of the etching processed parts on the device under test caused by the temperature increase during the repeated application of the etching operations in the etching process, it is necessary to control the temperature of the device under test during the etching process. Conventionally, this has been achieved by providing a cooler below the table from which the cooled water is circulated around the table in order to control the temperature of the device under test. However, this method makes the size of the apparatus very large and the cost of the apparatus very expensive. Also, in order to circulate the cooled water, the piping around the table is required, but such a piping interfered with the operations to be performed around the table.